The investigations on screening smokes have been directed toward the development of suitable devices for the protection of industrial and military objectives against aircraft by the use of large quantities of smokes or fogs. The subject is referred to in English reports as area screening. Because of the large areas of the industrial sites to be protected, the amounts of material required for screening purposes are so great that the usual chemical smokes such as white phosphorous, chlorsulfonic acid, etc. cannot be employed. Although the principal purpose is the protection against aircraft by making aimed bombing impossible, it appears from British reports that the use of protective smokes has been an important factor in maintaining the morale of factory workers, especially in munitions plants.